(a) Field of the Invention
Various exemplary embodiments of the present invention relates a fastening element. More particularly, the present invention relates to a rivet screw drill for mechanically fastening at least two panels.
(b) Description of the Related Art
Generally, fastening elements such as a bolt and nut, a rivet and so on are used for mechanically fastening bases such as metal or nonmetal panels, sheets and so on.
In mechanical connection using a rivet, an assembling hole is formed to bases, the rivet is inserted into the assembling hole, and then the rivet is plastically deformed to connect the bases.
In addition, a blind rivet has been used for connecting bases.
In joining between dissimilar materials such as aluminum and steel, limited methods are used for joining the bases because melting temperatures are various as well as design freedom is limited.
For overcoming the drawbacks described above, a FDS (Flow Drill Screw) has been used for fastening a plurality of panels. It is also called as a friction stir (blind) rivet.
For example, the FDS is comprised of a head portion mounted to a pressurizing/rotation device, a thread portion integrally formed with the head portion and of which screw thread is formed to an external circumferential surface thereof, and a perforating portion integrally formed with the thread portion and penetrating a panel.
However, especially when high-tensile steel sheets are assembled, free holes have to be formed to the sheets previously due to limitation of piercing characteristic of the FDS.
Thus, previous processes of piercing holes increases manufacturing costs and deteriorate productivity.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.